Microplastics pollution threatens Goa’s estuarine fisheries, human consumers

For Preliminary Examination:  Current events of national and international Significance like Plastic Pollution

For Mains Examination: GS III - Environment and Ecology

Context:

Researchers identified 4,871 polluting particles, of which 3,369 particles were plastic polymers of 19 types. Researchers found more contamination on the sea floor than in open water. Particles were mainly from fishing material and wastewater

Read about:

Single Plastic Use

Microplastic Pollution

Key takeaways:

• Microplastics present in aquatic environments can be consumed by microscopic organisms, which are then eaten by progressively larger species. This causes microplastics to build up in the bodies of animals higher in the food chain, increasing their overall exposure and toxic effects — a process known as bioaccumulation.
• To investigate how microplastics accumulate along the Goan coastline, researchers from the CSIR–National Institute of Oceanography (Goa) and the Academy of Scientific and Innovative Research (Ghaziabad) examined the feeding habits and habitats of 251 fish belonging to nine species of finfish and shellfish.
• Their samples included economically important species such as mackerel, anchovy, oyster, clam, catfish, and sardine, collected from varying ocean depths.
• Their findings, published in Environmental Research (August edition), identified 4,871 foreign particles within the sampled fish, out of which 3,369 were confirmed as plastic polymers representing 19 distinct types.
• The researchers observed higher concentrations of these particles on the sea floor and bottom sediments (benthic region) compared to the open-water (pelagic zone).
• Most of the detected plastics originated from discarded fishing gear and wastewater runoff from human settlements.
• According to the study, affected fish showed signs of genetic disruption, oxidative stress, reproductive impairment, and stunted growth. Humans consuming such fish could also face immune system disturbances, increased cancer risk, and neurological toxicity.
• Fishing activities around Goa are mainly concentrated in estuaries, which are ecologically vital zones supporting young fish and providing feeding areas for mature ones. These estuaries are rich in finfish and shellfish, species that are popular in Indian diets for being nutritious, affordable, and easily available.
• Small pelagic species such as anchovies, sardines, and mackerel are central to estuarine food chains. They feed on plankton and attract larger predators. As filter feeders, they trap particles from surrounding water, making them especially prone to microplastic ingestion.
• These smaller fish are preyed upon by larger species, including elasmobranchs like sharks, which dwell in coastal shelf waters. Through this trophic transfer, microplastics gradually travel up the food web, ultimately reaching apex predators and humans.
• The study focused on fish from the Mandovi estuarine system, part of the Mandovi–Zuari network, which accounts for nearly 97% of Goa’s total fish production. Researchers used the bamboo shark, an apex predator, to examine the long-term impacts of microplastic accumulation.

This work addressed five key research gaps:

• Levels of microplastic contamination in commercially important fish;

• Factors influencing microplastic uptake;

• The main body parts through which ingestion occurs;

• Evidence of ingestion in the bamboo shark; and

• The health implications for both marine life and human consumers along Goa’s coast.

• To explore these questions, scientists analyzed 30 specimens each of mackerel, sardine, anchovy, bamboo shark, sole fish, catfish, clam, and oyster, and 11 green mussels. They grouped the species according to feeding behavior — filter feeders, planktivores, secondary consumers, and carnivores — and measured microplastic levels in their soft tissues.
• Results showed that anchovies had the highest concentration among pelagic species, with 8.8 microplastic particles per fish, while catfish led the benthic group with over 10 particles per fish. The bamboo shark contained the least, at 3.5 particles per fish, while seawater samples recorded 120 microplastic particles per litre.
• Interestingly, smaller fish tended to accumulate more microplastics, and those living closer to contaminated sediments ingested higher quantities.
• Among finfish, more microplastics were detected in the digestive tract than in the gills, suggesting ingestion through food and water. As water passes through gills, particles may also become trapped, causing potential respiratory stress.
• The study identified four main shapes of microplastics — fibres (53%), fragments (29.9%), films (13.1%), and beads (4%) — appearing in nine colors, most commonly blue (37.6%), black (24.3%), and red (12%). The colors and forms helped trace their origins to fishing nets, tyre residue, electronic waste, packaging materials, and textiles.
• In terms of environmental impact, the research categorized Goa’s marine region as low-risk overall, but found that benthic species are more vulnerable than pelagic ones. Out of the 19 polymer types, 11 were identified as highly toxic.
• Furthermore, 66 of the 71 shellfish species studied displayed poor nutritional quality, echoing previous research that links microplastic contamination to reduced protein, fatty acid content, and overall fitness in fish.

 Follow Up Question

Mains

1.Microplastic contamination in marine ecosystems poses a serious threat not only to aquatic biodiversity but also to human health and coastal livelihoods. Discuss the findings and implications of recent studies on microplastic bioaccumulation along the Goan coast in this context. Suggest measures to mitigate microplastic pollution in India’s coastal waters

Prelims